Isotope concentration process



Patented July 3, 1951 UNITED STATES PATENT OFFICE ISOTOPE CONCENTRATIONPROCESS Jersey No Drawing. Application February 4, 1948, Serial No.6,346

3 Claims. 1

This invention relates to the preparation of a catalyst or contact masssuitable for use in chemical operations generally, specifically in theconcentration of isotopes, as will appear hereinafter, and to the novelcatalyst or contact mass thus prepared.

In Serial No. 534,023 filed May 4, 1944, by Allen F. Reid, now PatentNo. 2,435,796, there is described and claimed a process for the relativeconcentration of isotopes of carbon and oxygen comprising reactionbetween carbon dioxide, carbonic acid, bicarbonate ion and water inpresence of a heterogeneous catalyst packing containing a member of thegroup consisting of silicon oxide, a silicate, carbon and aluminumoxide. The reaction is effected by flowing carbon dioxide into themixture of carbon dioxide, carbonic acid, bicarbonate ion and water atcertain there described rates. A fluid enriched in the desired isotopesof carbon and/ or oxygen is taken off the catalyst or contact mass.

The catalysts mentioned in the above-identified application are asfollows: etched siliceous shale, etched Pyrex (a heat resistant glass)helices, calcined silica gel, lead carbonate on aluminum oxide, aluminumoxide, charcoal and fiber glass.

The necessity for the foregoing catalysts or contact masses is madeapparent in said applica tion. Thus, it was not until heterogeneouscatalysis was applied to isotope concentration of this sort thatequilibrium concentrations of the desired isotopes could be attainedwith a reasonably sized plant and within a period of time which was notprohibitory. As set forth in said application the approach toequilibrium, of the several reactions which take place, occurs very.slowly in the absence of a suitable catalyst or contact mass. Such acatalyst or contact mass must have a large surface area and must be suchas to cause close contact between the gaseous and liquid phases extantin the system. 7

According to this invention we have found that an improved contact towerpacking, which will yield improved results in the isotopic concentrationof carbon and oxygen, can be prepared from aluminum treated with asolution containing essentially a sodium silicate. The aluminum shouldbe in a sub-divided form and will ordinarily be in the shape of rings,saddles, coils, spirals, blocks, grids, wire, tubes or other shapesfound useful in countercurrent operation between a liquid and a gas.

Thus, according to this invention the aluminum material is treated witha water solution 2 containing essentially an alkali silicate. Whensodium silicate is employed, the ratio of NazO to $102 will bepreferably in the range of 25Na2O2 18102 to lNazOzSiOz. Much higherratios can be employed. The solution of the silicate is made preferablywith water. The concentration of the sodium silicate in the watersolution can be varied. However, this concentration must not be suchthat the solution becomes too viscous, at the temperature of treatment,to permit of a mild agitation.

The treated aluminum is found to possess a catalytic surface which isstrongly adherent, abrasion resistant and insoluble in the bicarbonatesolution which is used in the isotope concentration process.

The conditions of the treatment of the aluminum with the aforementionedsilicate solution can be varied but due care must be exercised in theirselection and correlation.

As already stated, the ratios of NazO to S102 can be varied. Thetemperature can also be varied. Thus, the temperature can be as low asdesired provided that the solution employed is not too viscous at thetemperature of treatment to accomplish desired agitation. Also, the temperature can approach the boiling point of the said solution.

The time of the treatment of the aluminum with any particular solutionof sodium silicate will depend upon its concentration and temperature aswell as upon the degree of agitation. Other factors to be considered arethe size and roughness of the aluminum particles and the ratio of thesolution to the metal. Aluminum rings or helices suited for the isotopicconcentration processes discussed herein have been prepared in less thanabout one hour contact time. It is clear that one versed in the art canreadily determine when the aluminum surface has been treated to asuflicient extent. Accordingly, the invention is not to be limited toany particular time of contact between the aluminum and the sodiumsilicate solution.

The agitation is required to ensure exposure of all of the surfaces ofeach piece of aluminum to the action of the treating solution in orderto accomplish a substantially uniformly prepared surface. The agitationshould be mild so that the coating being formed is not destroyed ordamaged V ininum silicate.

have any practical temper and purity. As stated, it is used in variousshapes or sub-divided form. It is usually necessary, for best results tobe obtained, to preclean the surfaces of the alu minum to be used. Thus,when the surface of the aluminum is oily or has other organic materialupon it, it can be washed with a water soluble organic solvent, such asacetone, or in any other satisfactory manner. Any traces of organicsolvent can be washed away with water prior to the treatment with thesodium silicate solution. If there is present on the surfaces of thealuminum matter which cannot be washed off, it can be abraded on bytumbling the aluminum pieces, pellets or other shaped particles alone,or together with a suitable abrasive, such as emery dust. To preventexcessive wearing of thealuminum particles, these can be tumbledtogether with other masses also consisting of aluminum.

Example I Aluminum rings inch inside diameter, made from 22 gaugefull-hard-temper wire were immersed in boiling acetone for about /2 hourfollowing which the acetone was drained away and the rings washed withwater. A treating solution containing 90% water and 10% Na2SiO3.5H2O wasused. A volume of this solution, equal to about twice the solution ofthe rings to be treated, preheated to about 130 F. was then poured overthe rings. A reaction was thus initiated. This reaction was allowed toproceed for about 10 minutes with moderate agitation to prevent stickingof the rings to each other, thus ensuring uniformity in the coating.Following this treatment, the treating solution was drained a and thetreated rings were water-washed to remove all traces of said solution.The catalyst was then washed with acetone and air-dryed at about roomtemperature.

Example If The foregoing procedure was employed except that a solutioncontaining NazO and 8102 (1:3) at 70 F. was used. The reaction wasallowed to proceed. for 30 minutes.

Example III the aluminum with the sodium silicate is believed to consistessentially of an agglomerate of hy-. drates of aluminum oxide, siliconoxide and alu- Thus, .according to the invention there is formed acatalyst or contact mass having a metallic aluminum core covered with afilm consisting of a mixture of hydrates of aluminum oxide, siliconoxide and aluminum silicate.

It is obvious that other alkali silicates, such as potassium silicate,can be substituted for the sodium silicate. The silicates which can beused are readily determinable.

As stated, the catalyst or contact mass of the invention is particularlysuited to the relative concentration of isotopes of oxygen and ofcarbon. Thus, oxygen (17) and oxygen (18) and carbon (13) and carbon(14) can be concentrated. The concentration of other isotopes of oxygenand carbon is notexcluded. Likewise, it

will be readily obvious that the catalyst or contact mass of thisinvention can be used to prepare pure oxygen (16) or pure carbon (12).

Modification and variation are possible within the scope of the appendedclaims to the invention the essence of which is that a novel catalyst orcontact mass consisting essentially of aluminum coated with a mixture ofhydrates of aluminum oxide, silicon oxide and aluminum silicate has beenprepared employing a novel process comprising the step of treatingsub-divided aluminum with sodium silicate as aforedescribed.

We claim:

1. In the process of relatively concentrating isotopes of carbon and ofoxygen contained in compounds thereof by reacting carbon dioxide,carbonic acid, bicarbonate ion and water in the presence of aheterogeneous catalyst by flowing carbon dioxide into a, mixture ofcarbon dioxide, carbonic acid, bicarbonate ion and water, and taking ofifrom said heterogeneous catalyst a fluid enriched with the desiredisotope, the improvement which comprises employing as said heterogeneouscatalyst an aluminum packing which has been reacted with an alkalisilicate.

2. In the process of relatively concentrating isotopes of carbon and ofoxygen contained in compounds thereof by reacting carbon dioxide,carbonic acid, bicarbonate ion and water in the presence of aheterogeneous catalyst by flowing carbon dioxide into a mixture ofcarbon dioxide, carbonic acid, bicarbonate ion and Water, and taking offfrom said heterogeneous catalyst a fluid enriched with the desiredisotope, the improvement which comprises employing as the heterogeneouscatalyst an aluminum packing -which has been treated with a sodiumsilicate solution at a temperature in the range of from about roomtemperature to the boiling point of the solution, said sodium silicatesolution being employed as a water solution containing NazO and S102 ina ratio of from 25NazO:lSiOz to lNazO AS102.

3. In the process of relatively concentrating isotopes of carbon and ofoxygen contained in compounds thereof by reacting carbon dioxide,carbonic acid, bicarbonate ion and water in the presence of aheterogeneous catalyst by flowing carbon dioxide into a mixture ofcarbon dioxide, carbonic acid, bicarbonate ion and water, and taking offfrom said heterogeneous catalyst a fluid enriched with the desiredisotope, the improvement which comprises employing as said heterogeneouscatalyst a metallic aluminum core covered with a film consisting of amixture of hydrates of aluminum oxide, silicon oxide and aluminumsilicate.

' ARISTID V. GROSSE.

ALLEN F. REID.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Soluble Silicates in Industry, byVail, Chemical Catalog Co., 1928, pages 85, 86, 2'73, 2'74.

1. IN THE PROCESS OF RELATIVELY CONCENTRATING ISOTOPES OF CARBON AND OFOXYGEN CONTAINED IN COMPOUNDS THEREOF BY REACTING CARBON DIOXIDE,CARBONIC ACID, BICARBONATE ION AND WATER IN THE PRESENCE OF AHETEROGENEOUS CATALYST BY FLOWING CARBON DIOXIDE INTO A MIXTURE OFCARBON DIOXIDE, CARBONIC ACID, BICARBONATE ION AND WATER, AND TAKING OFFFROM SAID HETEROGENEOUS CATALYST A FLUID ENRICHED WITH THE DESIREDISOTOPE, THE IMPROVEMENT WHICH COMPRISES EMPLOYING AS SAID HETEROGENEOUSCATALYST AN ALUMINUM PACKING WHICH HAS BEEN REACTED WITH AN ALKALISILICATE.